1. Field of the Invention
The present invention relates to an apparatus and method for measuring the surface damage of a vehicle windshield using a digital imaging device.
2. Description of the Prior Art
Pitting and scratching of vehicle windshields has long been a problem that causes interference with operator vision and driving safety. "Direct Measurement of Windscreen Surface Wear and the Consequences of Road Safety" presented by A. Timmermann at the Conference on Vision in Vehicles, Nottingham, UK, 9-13 September 1985, presents an apparatus for measuring the light scatter of a localized beam of light as it passes through a vehicle windshield. It comprises a means for directing a parallel beam to a first light detector. A second light detector surrounding the first light detector at the focus point detects stray light that is diverted by the windshield surface damage. With Timmerman's device the ratio of stray light to direct light provides a measure of windshield damage. Timmermann's device yields exact measurements for localized windshield damage but requires expensive, specialized equipment. Further, significant time and effort is required in the use of Timmermann's device to assess the surface quality of a windshield.
Our investigations have shown that pitting varies widely across a windshield surface. Consequently, what is needed is a means for assessing pitting or surface damage over a large area of a windshield. We have found that a pattern of sample zones taken from a large area is an efficient and reliable means for assessing pitting or surface damage over a large area of a windshield. Further, we have found that values for pitting in pixels per square inch either on a worst case or on an average bases can be determined which correspond to a windshield having a unacceptable degree of surface damage or pitting.
Our investigations have also revealed that the peripheral glare produced by surface pitting in areas of the windshield opposite an operator's eye point can produce significant visual interference. A method and apparatus is needed to quickly assess windshield surface quality in windshield areas opposite the operator's eye point. Accordingly, what is needed is a method and apparatus for assessing windshield surface quality over large portions of a windshield surface and consequently what is also needed is a method and apparatus for assessing windshield surface quality in a windshield area opposite an operator's eye point.